1. Field of the Invention
The present invention relates to methods and apparatus for forming optical fiber and more particularly, to methods and apparatus for forming optical fiber having improved characteristics.
2. Technical Background
Optical fibers have acquired an increasingly important role in the field of communications, frequently replacing existing copper wires. This form of transmission is done by sending a beam of light through an optically clear fiber. Because interference with the light beam or its partial loss during the transmission must be at a minimum to make the use of optical fibers a successful communications technology, the optical fibers must be protected from any environment which will cause loss of signal or distortion of the signal. Coating the fibers is one such technique. The optical fibers are coated to protect the fiber surface from damage which can result from abrasion or water, to maintain the fiber strength, and to prevent transmission loss resulting from fiber bending.
Optical fibers typically contain a glass core, a glass cladding, and at least two coatings, i.e., a primary (or inner) coating and a secondary (or outer) coating. The primary coating which is applied immediately after the fiber is formed serves as a buffer to cushion and protect the glass fiber core when the fiber is bent, cabled, or spooled. The secondary coating is applied over the primary coating and functions as a tough, protective outer layer that prevents damage to the glass fiber during processing and use. Both coatings typically need to be cured (e.g., by irradiation with UV light) to harden and to maintain structural integrity through the fiber life time.
Conventional techniques and manufacturing processes for producing optical fibers generally include drawing an optical fiber downwardly along a linear pathway through the stages of production. However, this technique provides significant impediments to improving and modifying production of the optical fiber. For example, the equipment associated with linear production of optical fibers is usually aligned in a top to bottom fashion thereby making it difficult to add or modify the process without adding height to the overall system. In some cases, addition to the linear production system requires additional construction to add height to a building housing (e.g., where the draw tower is at or near the ceiling of an existing building). Such impediments cause significant costs in order to provide modifications or updates to optical fiber production systems and facilities.
For example, it is difficult to increase the draw speed of the fiber, because the fiber spends less time in UV irradiators that cure fiber coating. However, adding more irradiators or larger irradiators to the linear production system is difficult. There is typically little space available for adding additional irradiators (to accommodate a fiber that travels faster through the irradiator), without adding height to the overall system. Because adding height to an existing system can add significant cost to the system, fiber draw systems in which space is available for additional irradiators without necessitating an increase in overall system height are desired.